1. Field of the Invention
The invention relates to document transport devices for use in document handling machines, and particularly to document transport devices utilizing a conveyor belt for transporting documents on-edge in a vertically-oriented, upright position.
2. Related Art
Document handling machines which convey mail on-edge, that is, where the plane of the mail item is vertical while it is conveyed by a horizontal belt, are well-known. A document handling machine of this type is taught in commonly-assigned U.S. Pat. No. 4,955,596, which is incorporated herein by reference. Generally, such machines convey a series of envelopes between stations which perform various operations, such as bar-code reading, bar-code printing, and sorting.
Because mail items are delivered to the machine in stacks, a feeder which singulates the stacks of mail into a series of end-to-end, vertically oriented, individual items is required. This conversion step often uses a ninety-degree change of direction in the envelope path, which is accomplished by a series of feed rollers oriented so as to feed in a direction perpendicular to the feed path of incoming stacks of documents. This sudden change of direction requires great force when the machine is operating at high throughput speeds, and results in undesirable wear on the perpendicularly-oriented feed roller drive mechanism, the rollers themselves, and the documents being transported. The machines of the prior art do not provide a solution to this problem of undesirable wear. Further, the machines of the prior art have been plagued with the problem of misfeeds and excessive forces on the feeder mechanism, both of which are the result of multiple envelopes being delivered to the feeder simultaneously.